SCIENCE
NERVOUS SYSTEM
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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the spread of action potential down the axon
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along myelinated axons it moves at a speed of about 18-140 meters per second (18-140 mph)
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along unmyelinated axons it moves at a speed of about 1 meter per second (2 mph)
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None of the above
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Detailed explanation-1: -By acting as an electrical insulator, myelin greatly speeds up action potential conduction (Figure 3.14). For example, whereas unmyelinated axon conduction velocities range from about 0.5 to 10 m/s, myelinated axons can conduct at velocities up to 150 m/s.
Detailed explanation-2: -In neuroscience, saltatory conduction (from Latin saltus ‘leap, jump’) is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.
Detailed explanation-3: -Poor conductivity in the neuron cytosol limits electrical current signal velocity according to cable theory, to 1-3 m/s, whereas saltatory conduction occurs with a velocity of 100-300 m/s.
Detailed explanation-4: -Why is saltatory conduction along a myelinated axon faster than continuous conduction along an unmyelinated axon? a. Since there are many more voltage-gated channels located along a myelinated axon, the conduction rate all along the axon is more rapid than along an unmyelinated axon (which has fewer channels).